Vacuum metallizing of plastic and similar dielectric substrates is disclosed in various forms including U.S. Patents:
______________________________________ 2,992,125 Fustier 2,993,806 Fisher 3,118,781 Downing 3,914,472 Nakanishi 4,101,698 Dunning 4,131,530 Blum 4,211,822 Kurfman 4,215,170 Oliva ______________________________________
In addition, two reference books are:
Thin Film Phenomena, Kasturi L. Chopra, Robert E. Kreiger Publishing Company, Huntington, N.Y., 1979. pp. 163-189.
Handbook of Thin Film Technology, Leon I. Maissel and Reinhard Glang, McGraw-Hill Book Company, New York, N.Y., 1970. , pp. 8-32 to 8-43.
U.S. Pat. Nos. 4,407,871, 4,431,711 and 4,713,143, assigned to assignee of the present invention and incorporated herein by reference, relate to metallizing of plastic articles and more particularly to the structure and spacing of discrete metal islands used to metallize rather than a continuous metal film. The metallizing is performed utilizing the island coating system as detailed in the aforesaid patents. The system includes generally spray depositing sequentially a primer coating layer, a basecoat coating layer, a metallizing layer and a topcoat layer. As disclosed in the above referenced patents, the coating layers contain non-volatile film forming polymers, generally in the range of 10-30% requiring flash time of 20 minutes at ambient temperature and cure times of approximately 30 minutes at 260.degree. F. between application of layers.
In addition to proper deposition of the coating layers, the appearance and performance of the commercial product, the conductivity of the metal layer, the corrosion resistance of the metal layer and/or the adhesion of the top coat all relate to the structure and spacing of the islands. The above referenced patents provide further teachings related to nucleation and film growth to the desired island structure and spacing that achieves these ends.
In U.S. Pat. No. 5,290,625, assigned to the assignee of the present invention and incorporated herein by reference, the above process is applied to aluminum parts. In a copending application, U.S. Ser. No. 08/248,957, assigned to the assignee of the present invention and incorporated herein by reference, the coating layers are modified to form a combined primer/basecoat layer. The underlying combined primer/basecoat can include a pigment to provide a colored metallic appearance as disclosed in U.S. Pat. No. 5,320,869 issued Jun. 14, 1994 and assigned to assignee of the present invention and incorporated herein by reference. In another copending application, U.S. Ser. No. 08/248,649, assigned to the assignee of the present invention and incorporated herein by reference, the technology for coating layer deposition is improved to allow film builds of 1.5 to 2.0 mils, eliminating significant coating irregularities.
The current island coating system spray deposits the polymeric constituents of the primer layer, basecoat layer and topcoat layer in organic solvent carriers such as glycol ethers, glycolether acetates, aromatic hydrocarbons and dibasic esters. These solvent carriers pose a waste disposal problem increasing the cost of production significantly, a flammability hazard, as well as requiring significant flash and cure times. If the organic solvents could be eliminated, while still maintaining the aesthetic properties of the metallized appearance, significant savings in time and therefore increased production, improved safety, as well as ease of waste disposal would be attained. Additionally, with the elimination of organic solvents the range of substrates that can be metallized could be increased.
In general, the step of spray depositing is done for batch processing while the parts are being rotated as described in U.S. Pat. No. 5,284,679 issued Feb. 8, 1994 and assigned to the assignee of the present invention, and incorporated herein by reference. However, the use of rotation is not practical when dealing with substrates that are thin sheets such as thin extruded polymers, cellulose based materials and textiles. These thin gauge sheets or sheetstocks require different handling and for high speed production it would be useful to be able to have continuous in-line processing.
Apparel designers would find it advantageous to have a metallized sheetstock made from various materials such as polymers, vinyls, cellulose based materials and textiles, that are flexible, washable, formable, and die cutable. Currently available metallic trims are generally either not truly metallic in appearance, or upon washing and wetting lose metallic luster or cannot be washed at all. Further, it would be advantageous to have materials with a metallized appearance that can be "ironed on", i.e. a thermal bonding adhesive, in addition to "stitched on". As one example, athletic shoe manufacturers have a perceived need to individualize their products with unique, identifiable features, as for example lights that are present on one brand of athletic shoes. Metallic trim would be useful in creating such identifiable features.
It would be useful to have thin polymer extrusion metallic finish products that can be cut on high speed electrically resisted die blades without arcing. Further it would be useful to be able to utilize such materials as exterior trim without corrosion and which can be used for in-mold decorating and which have the proper reflectivity or depth of image.